The present invention relates to semiconductor device fabrication and integrated circuits and, more specifically, to structures for the integration of a vertical field-effect transistor and a saddle fin-type field-effect transistor into an integrated circuit, as well as methods of integrating a vertical field-effect transistor and a saddle fin-type field-effect transistor into an integrated circuit.
Traditional transistor structures include a source, a drain, a channel situated between the source and drain, and a gate electrode configured to respond to a gate voltage by selectively connecting the source and drain to each other through the channel. Transistor structures are formed on a surface of a semiconductor substrate, which surface may be considered to be contained in a horizontal plane. Transistor structures can be broadly categorized based upon the orientation of the channel relative to the surface of the semiconductor substrate.
Planar transistors constitute a category of transistor structures in which the channels are oriented parallel to the substrate surface. Vertical transistors represent a different category of transistor structures in which the channels are aligned vertical to the substrate surface. Because the gated current between the source and drain is directed through the channel, different types of vertical transistors, namely fin-type field-effect transistors (FinFETs), and vertical field-effect transistors, can also be distinguished from each other based upon the direction of current flow. A FinFET has a horizontal channel in which the direction of the gated current flow between the source and drain of a FinFET-type vertical transistor is generally parallel (i.e., horizontal) to the substrate surface. In contrast, the direction of the gated current flow in the vertical channel between the source and drain in a vertical field-effect transistor is generally perpendicular (i.e., vertical) to the substrate surface.
Improved structures and fabrication methods are needed that integrate a vertical field-effect transistor and a saddle fin-type field-effect transistor in an integrated circuit.